From fb05e7a89f500cfc06ae277bdc911b281928995d Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Thu, 11 Jun 2015 16:50:48 -0700 Subject: [PATCH] net: don't wait for order-3 page allocation We saw excessive direct memory compaction triggered by skb_page_frag_refill. This causes performance issues and add latency. Commit 5640f7685831e0 introduces the order-3 allocation. According to the changelog, the order-3 allocation isn't a must-have but to improve performance. But direct memory compaction has high overhead. The benefit of order-3 allocation can't compensate the overhead of direct memory compaction. This patch makes the order-3 page allocation atomic. If there is no memory pressure and memory isn't fragmented, the alloction will still success, so we don't sacrifice the order-3 benefit here. If the atomic allocation fails, direct memory compaction will not be triggered, skb_page_frag_refill will fallback to order-0 immediately, hence the direct memory compaction overhead is avoided. In the allocation failure case, kswapd is waken up and doing compaction, so chances are allocation could success next time. alloc_skb_with_frags is the same. The mellanox driver does similar thing, if this is accepted, we must fix the driver too. V3: fix the same issue in alloc_skb_with_frags as pointed out by Eric V2: make the changelog clearer Cc: Eric Dumazet Cc: Chris Mason Cc: Debabrata Banerjee Signed-off-by: Shaohua Li Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/skbuff.c | 2 +- net/core/sock.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 3cfff2a3d651..41ec02242ea7 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -4398,7 +4398,7 @@ struct sk_buff *alloc_skb_with_frags(unsigned long header_len, while (order) { if (npages >= 1 << order) { - page = alloc_pages(gfp_mask | + page = alloc_pages((gfp_mask & ~__GFP_WAIT) | __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY, diff --git a/net/core/sock.c b/net/core/sock.c index 469d6039c7f5..dc30dc5bb1b8 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1880,7 +1880,7 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t gfp) pfrag->offset = 0; if (SKB_FRAG_PAGE_ORDER) { - pfrag->page = alloc_pages(gfp | __GFP_COMP | + pfrag->page = alloc_pages((gfp & ~__GFP_WAIT) | __GFP_COMP | __GFP_NOWARN | __GFP_NORETRY, SKB_FRAG_PAGE_ORDER); if (likely(pfrag->page)) {